Spring-actuated medical syringe



Nov. 1, 1955 STlG-AKE DAHLGREN 2,722,215

SPRING-ACTUATED MEDICAL SYRINGE Filed April 27, 1954 J INVENTOR. TIG ARE VAHLGREN B A TORNEY United States Patent 2,722,215 SPRlNG-ACTUATED MEDICAL SYRINGE Stig-Ake Dahlgren, Caracas, Venezuela Application April 27, 1954, Serial Na. 425929 6 Claims. 01. 12s 21s This invention relates td anew and improved springactuated medical syringe. The present invention has particular application in a pump-type syringe for self injection. The syringe has further application in injecting fluid in others, particularly where the user is relatively inexperienced. The foregoing features of the invention are occasioned by reason of the fact that there is provided a spring which projects the retractable needle with a fixed force and a fixed distance.

The present invention accordingly provides a syringe having an injection needle which may be retracted and, upon release of a trigger, propelled by a spring. This feature of the invention is particularly important in'as much as many users of common injection fluids encounter ditficulty and mental discomfort in injectinga needle into their own body and the same or similar difficulty is encountered by other persons in injecting needles into others. Accordingly, the present invention is a great convenience for persons who are not trained in the technique of in jection.

Another feature of the invention is the provision of means for holding the needle in position while the syringe is being filled.

Another object and advantage of the invention is the facility with which the device may be assembled and disassembled and sterilized.

Still another feature of the invention is the fact that the needle and a tube into which it retracts are separately installed and removeable as a unit.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings in which similar characters of reference represent corresponding parts in each of the several views.

In the drawings:

Fig. 1 is a top plan of the device.

Fig. 2 is a longitudinal vertical section taken substantially along the line 2-2 of Fig. 1.

Fig. 3 is a transverse section taken'substan tially along the line 3 -3 of Fig. 2. 1

Fig. 4 is an exploded view of the lower end of the needle retracting rod (partially broken away in section),

the needle holder and the needle.

Fig. 5 is an end view of the needle retracting rodtaken substantially in the direction of the line 5--5 of Fig. 4.

Fig. 6 is a transverse section takensubstantially along the line 6'-6 of Fig. 4.

The syringe comprises a barrel 21, preferably of a transparent material, to which are fitted upper and lower end caps 22 and 23. The depending skirt of upper end cap 22 is attached to the barrel with a bayonet slot connection, pins 24 projecting on the exterior of the barrel fitting within the conventional bayonet slots 26 in the upper cap 22. The upper end cap 22 has an enlarged central aperture 27 and a radially extending slot 28 which facilitates assembly of the apparatus as hereinafter set forth. The lower end cap 23 is externally tapered toward a truncated point 29 and is formed with an internal 2 cylindrical bore 31 terminating in a conical recess 32 at the bottom end for a purpose which hereinafter appears. The center of the lower end of the bottorn end ca provided with a hole 33 through which the needle 34 projects. L

Positioned centrally Within the barrel is a needle tube 36, the lower end of which is threaded into mating threads ontheinternal cylindrical bore 31 of thelowe'r end cap 23. The upper end of the needle tube is provided with a closure 37 threaded thereon, the closure having an upstanding knurled knob 38 to facilitate installation and removal of the closure. I t k I Surrounding the needle tube and slidably fitting within the barrel is an annular piston 39, the fit between the piston and the tube 36 and the piston and the barrel 21 being tight so as toreduce the danger of entrapment of air in the fluid which is drawn into the fluidchamber 41 between the needle tube and the barrel below the piston 37 as hereinafter set forth. Piston actuating arms 42 extend up through the central aperture 27 in the upper cap 22 and terminate in a handle 43 which enables the user to raise and lower the piston. The handle 43 is formed with a notch 44 extending inwardly from the center of one edge as shown particularly in Figs. 1 and 2 to provide clearance for rod 46.

A hollow pointed hypodermic needle 34 of conventional type is threaded into the lower end of needle carrier 47 which has a conical lower end complementary to the conical recess 32 in ,the bottom end cap 23. The needle carrier 47 fits slidably in the interior of the needle tube 36. Helical spring 48 is interposed between the closure 37 and the needle carrier 47, the strength of the spring being calibrated to project the needle 34 with the proper fixed force.

In order to retract the needle carrier, needle retract} ing rod 46 i's p'rovided to fit upward through a central aperture in closure 37, the upper end of rod 46 being bent outwardly to provide a grip 49. The upper end of the needle carrier 47 is provided with a round stud 51 having outwardly extending projections 52 spaced above the level of the top of the carrier. The lower end of the rod 46' is provided with a recess 53 having a diameter greater than the maximum distance across prejections 52, recess 53 having a restricted opening 514 complementary to the shape of the projections 52. This shape of the recess 53 and opening 54, as shown particularly in Figs. 5 and 6, provides shoulders 56 6151 the lower end of the rod 46 to support projections 52 when stud 51 on carrier 47 is received within recess 53'. When rod 46 is given a quarter-twist, rod 46 and needle carrier 47 are locked for axial movement together and by pulling rod 46 upwardly, the needle carrier may be moved upwardly in the needle tube 36 against the force of spring 48. v, ,7

Rod 46 carries radially extending pins 57, The pins 57 co-act with a pair of shoulders 58 formedas radially inwardly extending projections on the inside of short cylinder 59 affixed to the bottom of closure 37. As noted particularly in Fig. 3, the shoulders 58 have a restricted arcuate length considerably less than the full circumference of the cylinder 59' and thus when the lied 46 is positioned So that the pins 57 near firemen-da s; 58', as shown in dot-and-dash lines in Fig. 3, the red 46 may be retracted until the pins 57 are above the level of shoulders 58. When the rod is then given a quarter twist, the pins 57 rest on shoulders 5% and the needle carrier 47 is held in retracted position. Merely by twisting the rod 46 until the pins 57 clear the shoulders 58, as shown in the dot-and-dash position of Fig. 3, the trigger arrangement is released and the needle 34 expelled by the force of spring 48.

The outwardly bent grip 49 on upper end of the rod 46 coacts with hook 61 on the outside of upper end cap 22 so that when the rod 46 is turned to a position such that the grip 49 fits under the hook 61, the needle 34 and needle carrier 47 are held in projected position shown in solid lines in Fig. 2, thereby preventing the needle carrier 47 from getting out of proper position during filling of the syringe.

An upwardly extending axial channel 62 in needle carrier 47 aligned with hole 63 in needle 34 communicates with two circumferential slots 64 formed in the needle carrier 47 at difierent elevations. The slots 64 communicate with holes 66 in the needle carrier tube 36 when the needle 34 is fully projected and holes 66 align with upwardly extending channels 67 in the bottom end cap 23 which terminate in fluid chamber 41 between the needle tube 36 and the barrel 21.

In order to assemble the syringe, the upper end cap 22, piston 39, closure and spring 48 are removed. With the needle tube 36 screwed in position in the bottom end cap 23, needle carrier 47 and needle 34 are dropped through the upper end of tube 36 until they assume the position shown in Fig. 2. Spring 48 is installed behind needle carrier 47 and closure 37, which also carries the needle retracting rod 46, is screwed into the upper end of the needle tube. The piston 39 is then inserted around needle tube 36 and inside the barrel 21. Upper end cap 22 is installed by slipping the piston actuating arms 42 through the slot 28 and then securing the bayonet slot connection 24-26.

With the syringe assembled, the next step in the use thereof is filling chamber 41. The rod 46 is moved downwardly and the end is turned so that projections 52 on stud 51 fit on shoulders 56 and needle carrier 47 is secured to the rod 46. Rod 46 is turned until grip 49 is secured under hook 61. Thereupon, with the piston 39 in down position, the point of needle 34 is inserted in a container of fluid and the piston is raised by pulling upwardly on the handle 43 at the upper end of the piston-retracting arms 42. It will be understood, as is common in syringes of this type, that the proper quantity of fluid may be drawn into the chamber by the use of markings (not shown) on the transparent sides of the barrel 21.

After the syringe is filled, the next step is the retraction of the needle 34. This is accomplished by disengaging the grip 49 from the hook 61, pushing down and turning rod 46 so that the projections 52 on stud 51 fit on shoulders 56. The rod 46 is then drawn upwardly and turned until the pins 57 rest on shoulders 58 to maintain the needle 34 and needle carrier 47 in the retracted position. It will be noted that during retraction of the needle, no fluid is expelled from the chamber 41 because the slots 64 which communicate with the holes 66 in the needle tube are closed off as soon as the needle carrier is elevated above the position shown in solid lines in Fig. 2.

When it is desired to inject the fluid, the point 29 of the bottom end cap 23 is placed at the desired portion of the patients body and thereupon the grip 49 on the upper end of the rod 46 is twisted until the pins 57 clear the shoulders 58 which permits the spring 48 to propel the needle carrier 47 and needle 34 downwardly with a fixed force. The distance the needle 34 is projected is fixed by reason of the fact that the conical lower end of the needle carrier 47 seats against the conical seat 32 in bottom end cap. After the needle is inserted, the fluid is injected by pushing downwardly on the handle 43 connected to piston 39 which causes the fluid to flow downwardly through the channels 67, holes 66, slots 64 and channel 62 into the hole 63 in needle 34.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be practiced within the spirit of the invention and scope of the appended claims.

What is claimed is:

I. An automatic needle ejecting syringe comprising a barrel, an annular plunger in said barrel, means for moving said plunger longitudinally in said barrel, a needle carrier mounted inside said plunger having means for mounting a hollow needle, said carrier being formed with channels for fluid communication between the interior of a needle mounted thereon and the interior of said barrel, means for guiding said needle carrier for longitudinal movement inside said barrel, resilient means biasing said carrier toward needle projected position, means for retracting said needle against the force of said resilient means, and releasable latch means for latching said needle carrier in retracted position. i

2. An automatic needle ejecting syringe comprising a barrel, an annular plunger in said barrel, means for moving said plunger longitudinally in said barrel, a tube mounted in said barrel and parallel thereto and fitting within the aperture of said annular plunger, a cylindrical needle carrier slidable within said tube, said carrier having a socket for reception of a hollow needle and a channel communicating between said socket and the interior of said barrel, resilient means biasing said carrier downwardly in said tube to needle projected position, means for retracting said needle within said tube against the force of said resilient means, and releasable latch means for latching said needle carrier in retracted position.

3. A syringe according to claim 2 which further cornprises second releasable latch means for latching said needle carrier in projected position.

4. A syringe according to claim 2 which further comprises a detachable connection between said needle carrier and said means for retracting said needle carrier.

5. A syringe according to claim 2 in which said means for retracting said needle carrier comprises a rod disposed within said tube and extending up through the top thereof, and in which said latch means co'mpn'ses a shoulder fixed in position relative to said tube and having a retracted arcuate length and a pin on said rod arranged when in latched position to rest on said shoulder and when in unlatched position to clear said shoulder for longitudinal movement of said rod, said rod being twistable from latched to unlatched position.

6. A syringe according to claim 5 which further comprises a detachable connection between the lower end of said rod and the top of said needle carrier, said connection being detachable on twisting of said rod relative to said carrier.

References Cited in the file of this patent UNITED STATES PATENTS 159,192 Leiter Ian. 26, 1875 187,031 McMorries Feb. 6, 1877 1,845,036 Busher Feb .16, 1932 

